Safer, more potent TB shot for HIV-positive developed

Washington, Oct 24 (IANS) A new TB vaccine developed for HIV-positive people has been found to be safer and more potent than the current shots in pre-clinical trials.”AIDS and tuberculosis epidemics are now so intertwined in many parts of the world that we can’t win the fight against one of these diseases without also taking on the other,” said Marcus Horwitz, principal investigator and microbiologist at David Geffen School of Medicine, University of California, Los Angeles (UCLA).

The current vaccine against TB, called BCG, is administered to newborns in most countries in the world. However, in HIV-positive people, the vaccine can cause serious and even fatal disease later in life if HIV weakens the immune system, allowing the vaccine to multiply and spread throughout the body.

Horwitz and his team used an innovative method to limit the number of times the new vaccine can replicate in the body - just enough to stimulate the immune system to produce T-cells to fight future infection with tuberculosis bacillus, but not enough to overwhelm the immune system if it subsequently becomes weakened by HIV.

The research demonstrated that the new vaccine better protects guinea pigs from TB than the current vaccine. Guinea pigs are highly susceptible to infection with Mycobacterium TB, the bacterium that causes most cases of TB in humans, and they develop TB remarkably similar to that in humans.

Researchers also showed that the new vaccine is much safer than BCG in a severely immunocompromised animal host - mice with severe combined immunodeficiency (SCID mice) that completely lack an immune system, said an UCLA press release.

While the vaccine could be administered to anyone, it is specifically designed to be given to HIV-positive newborns and adults whose immune systems are still relatively intact and are therefore able to mount a good immune response to the vaccine, including persons on antiretroviral therapy.

The next step is to test the vaccine in humans. It will take several years of further study before the vaccine is available to the public, said the researchers.

These findings are scheduled for publication in the November edition of Infection and Immunity.